1. Field of the Invention
The present invention is generally related to the field of telecommunications. For example, the present invention may be applicable to mobile telecommunications, such as communication using wireless communication devices. In one example, the present invention can be applied to mobile communications as discussed and defined by the Third Generation Partnership Project (3GPP). More particularly, the present invention may be of use in procedures for emergency registrations as described in 3GPP TS 24.229.
2. Description of the Related Art
The term “implicit registration set” is not conventionally clarified for emergency public user identities. The emergency public user identities as Session Initiation Protocol (SIP) Uniform Resource Identifiers (URIs) are constructed from normal public user identities adding the “sos.” tag, but it is unlikely that distinct telephone (tel) URIs will be available for emergency registration, thus tel URIs used as normal public user identities will be reused as emergency public user identities as well. Generic mechanism to define implicit registration sets for emergency public user identities are conventionally absent. Direct mapping (i.e. add the “sos.” to all SIP URIs in the set and keep tel URIs unchanged) does not work as for emergency registration it is conventionally mandatory to implicitly register a tel URI, while it is not a requirement for “normal” registration. Also creating a “superset” by adding all SIP URIs with a “sos.” tag and the tel URI(s) is not feasible as the shared/not shared property of the tel URI must conventionally be kept, even if it is used as an emergency public user identity.
A solution such as a new URI parameter to have distinct tel URI is not conventionally acceptable, because it cannot conventionally be used in the case of callbacks received from a Public Safety Answering Point (PSAP) in a Circuit Switched (CS) network.